Method for manufacturing solar battery

ABSTRACT

The invention is aimed to prevent that fall of characteristic of a solar battery and producing yield caused by particles of powder condition generating from working part at laser beam process in the method producing the solar battery by laser beam process. The constitution of the invention is characterized by comprising: a first step forming the lower electrode and the semiconductor layer on the insulating substrate by laminating; a second step forming a protective film on surface of the semiconductor; a third step forming an opening portion at the semiconductor layer, or the semiconductor layer and the lower electrode by laser beam process after the second step; and a fourth step removing the protective film.

BACKGROUND OF THE INVENTION

The present invention relates to a method for producing a solar batteryhaving semiconductor film on insulating substrate, particularly to amethod for producing an integrated solar battery produced using laserbeam processing.

In recent years, a thin film solar battery in which non-monocrystalsilicon film is formed on an insulating substrate is getting attention.Here, the substance applied as non-monocrystal silicon is amorphoussilicon, microcrystal silicon, thin film polycrystal silicon, andcompound thereof. A thin film solar battery is characterized in thatproduction cost is kept low and material used for production is little.By using plastic film substrate having flexibility as an insulationsubstrate, shape of the solar battery is set freely. It is one ofimportant characteristics to make an integrated structure possible onthe insulation substrate, where desired voltage is obtained by dividingan element to plural elements on single substrate and connecting theelements in series. It is possible to use a substrate having aninsulating surface, for example a conductive substrate on which aninsulating film is provided.

Laser beam process is used widely for producing a solar battery ofintegrated structure. The laser beam process irradiates laser beamgathered on a certain area to a work piece, makes a hole by melting,evaporation, or scattering, performs melting, cutting off, and marking,and divides, thereby any shape can be processed by scanning laser beam.By this technique, separation of thin film can be performed withscribing width of equivalent width in high speed. The laser beam processis used even for means melting and connecting taking-out electrodes ofthe solar battery. Although the process is called bonding especially,the process is included in the laser beam process.

There has been technique of photolithography hitherto as a method forshape-processing pattern for the purpose of electrode and semiconductorlayer constituting solar battery. Patterning process of the solarbattery using the photolithography applies a resist to allover face ofthe work piece, exposes through a mask, and after that, a resist mask isformed at developing process. Next, area except masked area with theresist is etched by etching process, after that, the resist is peeledoff by alkali solvent, and cleaning and drying are performed, therebythe process is completed. The process has problems of complexity andmany process steps, long processing time, and high production cost.

The patterning process of the solar battery by laser beam process issimple and few in number of processes. It has a distinguishingcharacteristic that the processes are completed only by irradiatinglaser beam while scanning at a part desired to perform patterning.

The laser beam process irradiates laser beam, melts a part of workinstantly, and evaporates or scatters. At this time, material of thepart of work melted at high temperature is cooled while scattering orafter sticking at periphery, and becomes particles of powder condition.The particles of powder condition damage generating layer of the solarbattery at manufacturing process after the laser beam process, therebycauses one of decline in characteristic.

Here, producing process of the solar battery using laser beam process ofthe prior art will be described using FIGS. 2A to 2E. First, a lowerelectrode 202 is formed on a substrate 201, and on the lower electrode202, a semiconductor layer 203 being a generating of the solar batteryis formed as shown in FIG. 2A. Next, to make an integrated structure ofthe solar battery on the same substrate, the lower electrode layer andthe semiconductor layer are divided by laser beam process, and pluralsections are made. Divided parts 204 a and 204 b by laser beam processare shown in FIG. 2B. At the laser beam process, the semiconductor layerand the lower electrode of the divided portions are melted and scatteredby the laser beam. Particles 205 a, 205 b, and 205 c of powder conditiongenerated at this time scatter and stick on the semiconductor layer 203of periphery. The particles possibly get stuck in the semiconductorlayer 203.

After the laser beam process, insulating layers 206 a and 206 b areformed. This is because contact of the lower electrode and an upperelectrode is prevented when the conductive upper electrode is formed onthe divided portion. The state using thermosetting resin as insulatinglayer and forming with screen printing method is shown in FIG. 2C.Insulating thermosetting resin 208 is applied on a screen printing plate207, a squeegee 209 is moved to direction 210 from right to left of thefigure, and resin is printed at parts of the insulation layers 206 a and206 b. At the printing, the screen-printing plate 207 contacts thesemiconductor layer 203 and particles of powder condition, and pressesthe particles of powder condition against the semiconductor layer. Eventhe particles of powder condition stuck on surface of the semiconductorlayer are possibly taken in the semiconductor layer.

In the printing process, when the screen-printing plate is separatedfrom the semiconductor layer and further after the printing process,particles of powder condition possibly desorbs from surface ofsemiconductor layer or inside. Parts 212 a, 212 b, and 212 c where theparticles of powder condition are desorbed exist at the semiconductorlayer as shown in FIG. 2D.

Although the upper electrodes 213 a, 213 b, and 213 c are formed asshown in FIG. 2E after the printing process and drying process, at thistime, parts 215 b and 215 c where the upper electrode and the lowerelectrode contact are formed at parts 212 b and 212 c where the lowerelectrodes expose among the desorbed parts 212 a, 212 b, and 212 c.Since the upper electrode and the lower electrode contact at unit cells214 b and 214 c, characteristic of the solar battery such as releasevoltage decreases. At a part 212 a where the lower electrode is notexposed, a part 215 a where the upper electrode and the lower electrodeare close is formed. Although characteristic of the solar battery suchas release voltage does not decrease directly by cause of the close part215 a, damage caused by static electricity occurs easily at dealing as aproduct.

Although method forming insulation layer using screen printing method isdescribed in FIGS. 2A to 2E, in the case forming insulation layer byanother method or using another producing process of the solar battery,generation of the particles of powder condition can not be avoided aslong as the laser beam process is performed. Although particles ofpowder condition generated at laser beam process stick at semiconductorlayer and get in inside of the layer, the particles drop out by processforming the upper electrode, and the upper electrode contacts the lowerelectrode at forming the upper electrode.

As one means to reduce foreign bodies of fine particles, there is amethod adjusting condition of laser power, that is, feeding speed of apart of work in laser beam processing device. For example, means makinglaser power weak, that is, making feeding speed of the working portionfast may be used. However, particles of powder condition generated atlaser beam process can reduce using the means, however, it is impossibleto remove the entire particles. For example, although it is possible tomake the sizes small or to reduce numbers of particles of powdercondition 205 a, 205 b, and 205 c shown in FIG. 2B, it is impossible toremove the entire particles.

As another means to reduce foreign bodies of fine particles, a methodabsorbing particles of power condition generated at process in laserbeam processing device using absorbing mechanism. However, althoughmaterial of a part processed by laser melts and scatters instantly,scattering speed is considerably high and temperature is high. Becauseof that, removing the particles of powder condition before adhesion togenerating layer of the solar battery or removing the particles ofpowder condition stuck is not performed completely even by using strongabsorbing mechanism.

The invention is performed in view of the above-mentioned problem, anobject of the invention is to prevent decrease of characteristic of thesolar battery and production yield caused by particles of powdercondition generating from a part of work at laser beam process.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned problem, the constitution of theinvention is characterized by comprising: a first step forming the lowerelectrode and the semiconductor layer on the insulating substrate bylaminating; a second step forming a protective film on surface of thesemiconductor; a third step forming an opening portion at thesemiconductor layer, or the semiconductor layer and the lower electrodeby laser beam process after the second step; and a fourth step removingthe protective film.

Another constitution is characterized by comprising: a first stepforming the lower electrode and the semiconductor layer on theinsulating substrate by laminating; a second step forming a protectivefilm providing an opening portion on surface of the semiconductor byscreen-printing method; a third step forming an opening portion at thesemiconductor layer, or the semiconductor layer and the lower electrodeby laser beam process corresponding to the opening portion; and a fourthstep removing the protective film.

Although the protective film is formed of thermosetting resin, it isdesirable to form the protective film with thermosetting polyestersystem resin. The protective film can be removed without complex processby peeling an adhesive tape and the protective film at the same timeafter the adhesive tape is bonded to the protective film.

By providing the protective film at laser beam process, particles ofpowder condition generating from a part of work is prevented to stickdirectly at the semiconductor layer so that the semiconductor isprevented to damage. By removing the protective film after laser beamprocess, particles of powder condition gets in the inside of thesemiconductor layer and drops out by the forming process of the upperelectrode even at screen-printing process so that shortage of the lowerelectrode at forming the upper electrode is prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1E are views describing process producing a solar batteryusing protective film at laser beam process;

FIGS. 2A to 2E are views describing process producing a solar batteryusing laser beam processing method of the related art;

FIGS. 3A to 3D are graphs showing transmissivity and reflectance asinfluence to monocrystal silicon film by protective film;

FIGS. 4A and 4B are graphs showing output characteristic of solarbattery as influence to monocrystal silicon film by protective film;

FIGS. 5A and 5B are graphs showing spectral characteristic as influenceto monocrystal silicon film by protective film;

FIGS. 6A to 6E are views describing process producing a solar batteryusing protective film; and

FIGS. 7A and 7B are histograms showing comparison of productioncharacteristic by existence of protective film.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A mode for carrying out the invention will be described referring FIG.1A to 1E. First, a lower electrode 102 and a semiconductor layer 103 areformed on a substrate 101 as shown in FIG. 1A. Next, protective films106 a, 106 b, and 106 c are formed except places 107 a and 107 b wherelaser beam process is performed as shown in FIG. 1B. For the protectivefilms, thermosetting resin, for example, is printed usingscreen-printing method so as to form by thermosetting.

After forming the protective film, laser beam process is performed todivide the semiconductor layer 103 and the lower electrode 102 as shownin FIG. 1C. Divided portions 104 a and 104 b of the semiconductor layerand the lower electrode are formed by laser beam process. At laser beamprocess, particles of powder condition 105 a, 105 b, and 105 c meltedfrom the semiconductor layer 103 and the lower electrode 102 by laserbeam scatter and stick on protective films 106 a, 106 b, and 106 c.

After the laser beam process, the protective films 106 a, 106 b, and 106c are removed as shown in FIG. 1D. Although melting by organic solventis general in removing method of resin, it is difficult to melt only theprotective film selectively at producing process when another resin isalready formed on surface of substrate. On the other hand, whenthermosetting resin having elasticity easy in exfoliation is used forthe protective film, only protective film can be removed easily withoutcrush by method that adhesive tape is put on surface of the substrateand is peeled off, that is, peeling method. Such the peeling methodwithout using solvent can omit washing process, and can reduce process.Because the protective film and particles of powder condition stuck onthe protective film are removed at the same time, particles of powdercondition on the semiconductor layer 103 become nothing at all.

After removing the protective films, divided portions of thesemiconductor layer and the lower electrode are filled with insulators108 a and 108 b as shown in FIG. 1E. The insulators are formed ofthermosetting insulating resin, for example, using screen-printingmethod. Further upper electrodes 113 a, 113 b, and 113 c are formed tobecome a laminated structure. For example, the upper electrode 113 a ofa unit cell 114 a connects to the lower electrode 102 b of a unit cell114 b, and each unit cell is connected in series. The upper electrodesare formed of conductive resin, for example, using screen-printingmethod. At the same time, an ejecting electrode 116 of the lowerelectrode side and an ejecting electrode 117 of the upper electrode sideare formed. When process forming the protective films is used, contactof the semiconductor and the lower electrode is not generated at formingthe upper electrode because the semiconductor does not have parts whereparticles of powder condition are omitted. Characteristic of the solarbattery does not fall, and yield of product improves.

EMBODIMENTS Embodiment 1

In the embodiment, existence of influence to output characteristic ofthe solar battery by forming and peeling the protective film is shown.First, a translucent lower electrode and a non-monocrystal silicon layerare formed on a translucent substrate, and at a part on thenon-monocrystal silicon layer, protective films protecting thenon-monocrystal silicon layer from particles of powder conditiongenerating at laser beam process are formed. For the protective films,thermosetting resin of polyester system (STRIP MASK #228-T made by Asahichemical laboratory, Inc.) is used. After forming the protective films,the protective films are peeled by an adhesive tape after designatedtime.

After the process peeling the protective films, a part not forming theprotective films and a part forming and peeling the protective filmsexist, then, transmissivity and reflectance are measured at each part.Transmissivity at the part not forming the protective films is shown inFIG. 3A, transmissivity at the part forming and peeling the protectivefilms is shown in FIG. 3B, reflectance at the part not forming theprotective films is shown in FIG. 3C, and reflectance at the partforming and peeling the protective films is shown in FIG. 3D. Intransmissivity and reflectance, there is not difference between the partnot forming the protective films and the part forming and peeling theprotective films.

After the process peeling the protective films, an upper electrode isformed at each of the part not forming the protective films and the partforming and peeling the protective films to form the solar battery.After that, output characteristic of each solar battery is measured tocompare the characteristic. Output characteristic (I-V characteristic)of each solar battery is shown in FIGS. 4A and 4B, and spectralcharacteristic of each solar battery is shown in FIGS. 5A and 5B. Evenin output characteristic and spectral characteristic of each solarbattery, there is not difference between the part not forming theprotective films and the part forming and peeling the protective films.

By the experimentation, it is known that forming and peeling theprotective films on the non-monocrystal silicon layer does not influenceoutput characteristic of the solar battery produced using thenon-polycrystal silicon layer. The similar effect can be obtained evenat another process producing the solar battery.

Embodiment 2

In the embodiment, a non-monocrystal silicon solar battery of alaminated structure is produced on an elastic substrate, and comparisonof yield of final product is shown. Producing processes are shown inFIGS. 6A to 6E. First, ITO (Indium tin oxide) and GZO (Gallium additionzinc oxide) are filmed as translucent conductive material on translucentPEN (Polyethylene naphthalate) film substrate by spattering method toform a lower electrode. Thickness of the ITO layer and the GZO are setto 50 to 60 nm and 20 to 30 nm respectively. Non-monocrystal siliconlayers of each of conductive types of p, i, and n are coated to form agenerating layer of the solar battery. Thickness of the non-monocrystalsilicon layers is set to 300 to 800 nm, in the embodiment, 600 nm.

Next, the non-monocrystal silicon film and the lower electrode layer aredivided in order to form the laminating structure on the same substrate,and one unit of the solar battery is produced. The one unit of the solarunit means a part having one stage of pin junction. Although there is acase including conductive ejecting electrode in the pin junction, in theembodiment, the one unit of the solar battery is called unit cell.Protective films are formed in order to protect the generating layer ofthe solar battery from particles of powder condition.

A state forming protective films 601 a, 601 b, 601 c, and 601 d on thegenerating layer are formed is shown in FIG. 6A. In FIG. 6A, peripheryof the protective films shows the lower electrode portion and thegenerating layer portion. Thermosetting resin easy in peeling is usedfor the protective films to form using screen-printing method. In theembodiment, STRIP MASK #228-T made by Asahi chemical laboratory, Inc. isused for the thermosetting resin.

After forming the protective films, the protective films are dividedusing laser beam process as shown in FIG. 6B. The method dividing withlaser beam is called laser scribing. A divided portion 602 a is dividedto each unit cell, and a divided portion 602 b is divided to theperiphery portion and an external form of the solar battery. It is needto consider the following items for dimension design of space betweenthe divided portion and the protective film. Actual width of made bylaser beam process is about 0.1 mm. The width varies a little by kind offilm processed, laser power, and processing speed. Margin of alignmentshift at laser beam process is considered. Therefore, distance betweenprotective films provided at both side of the divided portion by thelaser beam process is need to set 0.2 mm or more at least. In the caseforming the protective film using thermosetting resin by screen-printingmethod, design of a screen-printing plate considering the dimension isneed. Since the object of the protective film is to prevent damage ofthe generating layer caused by particles of powder condition, it isdesirable to cover the generating layer part as far as possible and tomake space between the divided portion and the protective film by laserbeam process as small as possible. In the embodiment, distance betweenprotecting films provided at both sides of the divided portion by laserbeam process is set to 0.5 mm.

After the laser beam process, the protective films are peeled as shownin FIG. 6C. In the peeling process, a tape having stronger adhesion thanadhesion of the protective films to the generating layer is put, and thetape and the protective films are peeled at the same time.

The divided portions 602 a and 602 b are filled with insulating resin603 as shown in FIG. 6D. The reason is as the following. That is, whenthe upper electrode of the unit cell is formed so as to get over thedivided portion to connect to the lower electrode of adjacent unit cell,it is prevented to contact the lower electrode of the upper electrodeitself so that output falls. Insulating resin is formed usingthermosetting resin by screen-printing method.

After forming the insulating resin, conductive upper electrodes 604 a,604 b, 604 c, and 604 d are formed as shown in FIG. 6E. The conductiveupper electrode is formed using thermosetting resin containing silver orcarbon by screen-printing method. The upper electrode are connected thelower electrodes of the unit cell adjacent to laser-bonding portions 605b, 605 c, and 605 d. For example, the upper electrode 604 a of a unitcell 606 a is connected to the lower electrode of adjacent unit cell 606b at the laser-bonding portion 605 b. A rejecting electrode 607 a isconnected to the lower electrode of the unit cell 606 a by laserbonding, is ejected to upper side. After the laser bonding process, unitcells 606 a, 606 b, 606 c, and 606 d are laminated in series, and asolar battery having an ejecting electrode 607 a of the lower electrodeside and an ejecting electrode 607 b of the upper electrode sideelectrode is completed. By forming the protective films protecting thegenerating layer of the solar battery at laser beam process, damage ofthe generating layer by particles of powder condition can be prevented.The solar battery shows excellent characteristic, and production yieldof characteristic improves.

Histograms of Fill Factor (F.F) as product characteristic by existenceof the protective film of resin are shown in FIGS. 7A and 7B. FIG. 7Ashows in the case not having the protective film, and FIG. 7B shows thecase having the protective film. Yield is defined as that F.F is largerthan 0.65 at characteristic of the solar battery of low illuminance 200lux. Although characteristic of the solar battery does not almost changeas shown in Embodiment 1, it is shown that effect of the protectivefilms appears largely in yield.

There is the following characteristic when screen-printing on theprotective film is possible and thermosetting resin easy in peeling isused. First, the resin has viscosity enabling to perform screen-printingprocess similarly as another thermosetting resin, and the desired shapecan be obtained by pattern hole plate. Because drying (curing)temperature is low, it is hard to generate damage to another film andchange in quality of material by temperature. Cure of the resin isperformed by volatizing solvent component at low temperature baking ofsome degree. The cured resin is peeled with simple contact. For example,an adhesive tape is used. Since adhesion of the resin and face of theprotective film is weak, damage does not appear at surface of theprotective film so that peeling is possible. At this time, since resinhas flexibility, resin itself is not crushed at peeling operation of theresin, and new fine particles are not increased. Like this, sincethermosetting resin easy in peeling is possible to perform the similarscreen-printing as usual printing process and is removed easily atpeeling process, it is possible to use as mask material of various uses.The present invention can be applied to not only the solar battery butalso other photovoltaic devices and semiconductor devices.

As described above, particles of powder condition generated from workingpart can be removed easily at laser beam process by using the presentinvention in patterning process of the solar battery by laser beamprocess. In producing process after laser beam process, characteristiccan be improved without damage of the generating layer of the solarbattery. Further, in product, product yield of characteristic can beimproved.

1. A method for manufacturing a semiconductor device comprising: forminga film over a substrate, the film having a lower surface and an uppersurface; forming an insulating film on the upper surface of the film,the insulating film having at least one opening portion; forming atleast one second opening portion corresponding to the first openingportion at the film by laser beam; and removing the insulating film. 2.The method according to claim 1, wherein the film is a semiconductorfilm.
 3. The method according to claim 1, wherein the insulating filmcomprises a thermosetting resin.
 4. The method according to claim 1,wherein the insulating film comprises a thermosetting polyester resin.5. A method for manufacturing a semiconductor device comprising: forminga film over a substrate, the film having a lower surface and an uppersurface; forming a mask on the upper surface of the film, the maskhaving at least one opening portion; forming at least one second openingportion at the film by using laser beam and the mask; and removing themask.
 6. The method according to claim 5, wherein the film is asemiconductor film.
 7. The method according to claim 5, wherein theinsulating film comprises a thermosetting resin.
 8. The method accordingto claim 5, wherein the insulating film comprises a thermosettingpolyester resin.
 9. A method for manufacturing a semiconductor devicecomprising: forming a film over a substrate, the film having a lowersurface and an upper surface; forming a mask on the upper surface of thefilm; patterning the film by using laser beam and the mask; and removingthe mask film.
 10. The method according to claim 9, wherein the film isa semiconductor film.
 11. The method according to claim 9, wherein theinsulating film comprises a thermosetting resin.
 12. The methodaccording to claim 9, wherein the insulating film comprises athermosetting polyester resin.
 13. A method for manufacturing asemiconductor device comprising: forming a film over a substrate, thefilm having a lower surface and an upper surface; forming an insulatingfilm on the upper surface of the film by printing method, the insulatingfilm having at least one opening portion; forming at least one secondopening portion corresponding to the first opening portion at the filmby laser beam; and removing the insulating film.
 14. The methodaccording to claim 13, wherein the film is a semiconductor film.
 15. Themethod according to claim 13, wherein the printing method isscreen-printing method.
 16. The method according to claim 13, whereinthe insulating film comprises a thermosetting resin.
 17. The methodaccording to claim 13, wherein the insulating film comprises athermosetting polyester resin.
 18. A method for manufacturing asemiconductor device comprising: forming a film over a substrate, thefilm having a lower surface and an upper surface; forming a mask on theupper surface of the film by printing method, the mask having at leastone opening portion; forming at least one second opening portion at thefilm by using laser beam and the mask; and removing the mask.
 19. Themethod according to claim 18, wherein the film is a semiconductor film.20. The method according to claim 18, wherein the printing method isscreen-printing method.
 21. The method according to claim 18, whereinthe insulating film comprises a thermosetting resin.
 22. The methodaccording to claim 18, wherein the insulating film comprises athermosetting polyester resin.
 23. A method for manufacturing asemiconductor device comprising: forming a film over a substrate, thefilm having a lower surface and an upper surface; forming a mask on theupper surface of the film by printing method; patterning the film byusing laser beam and the mask; and removing the mask film.
 24. Themethod according to claim 23, wherein the film is a semiconductor film.25. The method according to claim 23, wherein the printing method isscreen-printing method.
 26. The method according to claim 23, whereinthe insulating film comprises a thermosetting resin.
 27. The methodaccording to claim 23, wherein the insulating film comprises athermosetting polyester resin.